U.S. patent application number 16/439254 was filed with the patent office on 2019-12-19 for ultrasonic inspection system.
The applicant listed for this patent is Hitachi-GE Nuclear Energy, Ltd.. Invention is credited to Hiroshi HANAKI, Naoyuki KOUNO, Tetsuya MATSUI, Hiroshi OKAZAWA, Shinobu OOKIDO, Akinori TAMURA.
Application Number | 20190383604 16/439254 |
Document ID | / |
Family ID | 68839780 |
Filed Date | 2019-12-19 |
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United States Patent
Application |
20190383604 |
Kind Code |
A1 |
TAMURA; Akinori ; et
al. |
December 19, 2019 |
Ultrasonic Inspection System
Abstract
An ultrasonic inspection system includes an ultrasonic sensor
which includes a piezoelectric element to transmit and receive an
ultrasonic wave and a calibration piece, and a control device. The
calibration piece includes a propagation portion extending along an
upper surface of the piezoelectric element, and a propagation
redirecting portion which is formed on one side in an extending
direction of the propagation portion, and is connected to the
piezoelectric element through a heat resistant adhesive. The
propagation redirecting portion includes a slope inclined in a
vertical direction to the upper surface of the piezoelectric
element. The propagation redirecting portion is configured to
reflect the ultrasonic wave incident on the propagation redirecting
portion from the piezoelectric element on the slope and emit the
ultrasonic wave toward the propagation portion, and reflect the
ultrasonic wave which is reflected on an end surface on the other
side in the extending direction of the propagation portion and
incident on the propagation redirecting portion from the
propagation portion on the slope and emit the ultrasonic wave
toward the piezoelectric element.
Inventors: |
TAMURA; Akinori; (Tokyo,
JP) ; KOUNO; Naoyuki; (Tokyo, JP) ; MATSUI;
Tetsuya; (Tokyo, JP) ; OOKIDO; Shinobu;
(Hitachi, JP) ; HANAKI; Hiroshi; (Hitachi, JP)
; OKAZAWA; Hiroshi; (Hitachi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi-GE Nuclear Energy, Ltd. |
Hitachi-shi |
|
JP |
|
|
Family ID: |
68839780 |
Appl. No.: |
16/439254 |
Filed: |
June 12, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01B 17/02 20130101 |
International
Class: |
G01B 17/02 20060101
G01B017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2018 |
JP |
2018-112535 |
Claims
1. An ultrasonic inspection system, comprising: an ultrasonic
sensor which includes a piezoelectric element to transmit and
receive an ultrasonic wave and a calibration piece; and a control
device which calibrates a time axis on the basis of a propagation
time of the ultrasonic wave propagating in the calibration piece
and a sound speed of the calibration piece, and calculates a
thickness of a subject on the basis of a propagation time of the
ultrasonic wave propagating in the subject and a sound speed of the
subject, wherein the calibration piece includes a propagation
portion which extends along a surface of the piezoelectric element
on a side opposite to the subject, and a propagation redirecting
portion which is formed on one side in an extending direction of
the propagation portion, and is connected to the surface of the
piezoelectric element through a contact medium, and wherein the
propagation redirecting portion includes a slope inclined in a
vertical direction to the surface of the piezoelectric element,
reflects the ultrasonic wave incident on the propagation
redirecting portion from the piezoelectric element on the slope and
emits to the propagation portion, reflects the ultrasonic wave on
the slope which is reflected on an end surface on another side in
the extending direction of the propagation portion and incident on
the propagation redirecting portion from the propagation portion
and emits to the piezoelectric element.
2. The ultrasonic inspection system according to claim 1, wherein
the propagation portion of the calibration piece has a first end
surface and a second end surface which are different in a
propagation distance of an ultrasonic wave from the slope of the
propagation redirecting portion, wherein the control device
calculates the sound speed of the calibration piece based on a
propagation time and a propagation distance of the ultrasonic wave
reflected on the first end surface of the propagation portion of
the calibration piece, and corrects the sound speed of the subject
on the basis of the sound speed of the calibration piece, and
wherein the time axis is calibrated on the basis of a propagation
time and a propagation distance of the ultrasonic wave reflected on
the second end surface of the propagation portion of the
calibration piece, and the sound speed of the calibration
piece.
3. The ultrasonic inspection system according to claim 1, wherein
the calibration piece includes at least two propagation portions,
and at least one propagation direction changing unit disposed
between the propagation portions, wherein the propagation direction
changing unit is configured to include a slope inclined in a
parallel direction to the surface of the piezoelectric element,
reflect the ultrasonic wave incident on the propagation direction
changing unit from one propagation portion on the slope and emit
the ultrasonic wave toward another propagation portion, and reflect
the ultrasonic wave incident on the propagation direction changing
unit from the other propagation portion on the slope and propagate
the ultrasonic wave toward the one propagation portion.
4. An ultrasonic inspection system, comprising: an ultrasonic
sensor which includes a piezoelectric element to transmit and
receive an ultrasonic wave and a calibration piece; and a control
device which calibrates a time axis on the basis of a propagation
time of the ultrasonic wave propagating in the calibration piece
and a sound speed of the calibration piece, and calculates a
thickness of a subject on the basis of a propagation time of the
ultrasonic wave propagating in the subject and a sound speed of the
subject, wherein the calibration piece includes a propagation
portion which extends along a surface of the piezoelectric element
on a side opposite to the subject, a first propagation redirecting
portion which is formed on one side in an extending direction of
the propagation portion, and is connected to the surface of the
piezoelectric element through a contact medium, a second
propagation redirecting portion which is formed on the other side
in the extending direction of the propagation portion, and is
connected to the surface of the piezoelectric element through the
contact medium, wherein the first propagation redirecting portion
is configured to include a first slope inclined in a vertical
direction to the surface of the piezoelectric element, reflect the
ultrasonic wave incident on the first propagation redirecting
portion from the piezoelectric element on the first slope, and emit
to the propagation portion, and wherein the second propagation
redirecting portion is configured to include a second slope
inclined in the vertical direction to the surface of the
piezoelectric element, reflect the ultrasonic wave incident on the
second propagation redirecting portion from the propagation portion
on the second slope, and emit the ultrasonic wave toward the
piezoelectric element.
5. The ultrasonic inspection system according to claim 4, wherein
the calibration piece includes at least two propagation portions,
and at least one propagation direction changing unit disposed
between the propagation portions, wherein the propagation direction
changing unit is configured to include a slope inclined in a
parallel direction to the surface of the piezoelectric element, and
reflect the ultrasonic wave incident on the propagation direction
changing unit from one propagation portion on the slope and emit
the ultrasonic wave toward the other propagation portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to an ultrasonic inspection system
which measures a thickness of a subject.
2. Description of the Related Art
[0002] Ultrasonic inspection, which is one of non-destructive
examination technologies, has a low cost and ease of application,
and thus is employed in a wide range of fields. In nuclear power
plants, thermal power plants and chemical plants, the ultrasonic
inspection for measuring the thickness of pipes and containers is
periodically performed to ensure the soundness thereof.
Specifically, after removing a heat insulating material from the
pipe and the container, an ultrasonic sensor is pressed against a
predetermined inspection point to perform the ultrasonic
inspection. Therefore, it is necessary to attach and detach the
heat insulating material before and after inspection. If the
inspection place is at a high place, it is necessary to assemble
and remove a foothold before and after inspection. In addition,
since the ultrasonic sensor is manually pressed against the pipe
and the container, it is necessary to carefully arrange the
ultrasonic sensor so that a propagation direction of ultrasonic
waves is appropriate. Nuclear power plants require a great deal of
labor and time to inspect a large number of pipes and
containers.
[0003] For example, there is proposed a method in which the
ultrasonic sensor is fixed to the surface of a pipe under the heat
insulating material in advance. With this method, the ultrasonic
inspection can be performed without attaching or detaching the heat
insulating material. In addition, if the ultrasonic inspection is
performed during the operation of the plant, it is possible to
reduce a load of a periodic inspection. However, in the method, the
ultrasonic sensor is fixed to the surface of the pipe under the
heat insulating material. Therefore, it is hard to calibrate the
machine before and after the measurement while preparing a
calibration plate separately as in the related art. Therefore,
there is disclosed a method for assembling a calibration plate with
known material and thickness to the ultrasonic sensor (for example,
JP 2015-078910 A).
[0004] An ultrasonic wave measurement device disclosed in JP
2015-078910 A includes the ultrasonic sensor fixed to the surface
of the pipe and a flew detector. For example, as illustrated in
FIG. 7 of JP 2015-078910 A, the ultrasonic sensor includes a
piezoelectric element which transmits and receives the ultrasonic
wave, and the calibration plate which is fixed to the upper surface
(that is, a surface on the opposite side of the pipe) of the
piezoelectric element. The flew detector calculates a thickness of
the pipe on the basis of a propagation time of the ultrasonic wave
reflected one time on the inner surface (that is, a surface on the
opposite side of the piezoelectric element) of the pipe. In
addition, since the thickness and the material of the calibration
plate are already known, the flew detector calibrates a time axis
on the basis of the propagation time of the ultrasonic wave
reflected one time on the upper surface (that is, a surface on the
opposite side of the piezoelectric element) of the calibration
plate.
SUMMARY OF THE INVENTION
[0005] The technique in the related art described above has the
following problems. For example, as illustrated in FIG. 8B of JP
2015-078910 A, in a case where the calibration plate is relatively
thin, a reception timing of the ultrasonic wave reflected one time
on the upper surface of the calibration plate comes earlier than a
reception timing of the ultrasonic wave reflected one time in the
inner surface of the pipe. Therefore, the reception timing of the
ultrasonic wave (so-called multiple reflection wave) reflected
plural times on the surface of the calibration plate is overlapped
with or approaches the reception timing of the ultrasonic wave
reflected one time in the inner surface of the pipe, and thus the
former ultrasonic wave is likely to influence on the latter
ultrasonic wave. Therefore, the thinning of the ultrasonic sensor
can be achieved, but the measurement accuracy of the thickness of
the pipe is degraded.
[0006] On the other hand, as illustrated in FIG. 8A of JP
2015-078910 A, in a case where the calibration plate is relatively
thick, a reception timing of the ultrasonic wave reflected one time
on the upper surface of the calibration plate comes later than a
reception timing of the ultrasonic wave reflected one time in the
inner surface of the pipe. Therefore, the reception timing of the
ultrasonic wave reflected plural times on the surface of the
calibration plate comes further later than the reception timing of
the ultrasonic wave reflected one time in the inner surface of the
pipe, and thus the former ultrasonic wave does not influence on the
latter ultrasonic wave. Therefore, the measurement accuracy of the
thickness of the pipe can be secured, but the thinning of the
ultrasonic sensor is degraded.
[0007] The invention has been made in view of the above problems,
and an object thereof is to provide an ultrasonic inspection system
which can achieve both the thinning of the ultrasonic sensor and
the securing of measurement accuracy of the thickness of the
subject while the calibration piece is assembled to the ultrasonic
sensor.
[0008] In order to achieve the object, according to a
representative aspect of the invention, there is provided an
ultrasonic inspection system. The ultrasonic inspection system
includes an ultrasonic sensor which includes a piezoelectric
element to transmit and receive an ultrasonic wave and a
calibration piece and a control device which calibrates a time axis
on the basis of a propagation time of the ultrasonic wave
propagating in the calibration piece and a sound speed of the
calibration piece, and calculates a thickness of a subject on the
basis of a propagation time of the ultrasonic wave propagating in
the subject and a sound speed of the subject. The calibration piece
includes a propagation portion which extends along a surface of the
piezoelectric element on a side opposite to the subject, and a
propagation redirecting portion which is formed on one side in an
extending direction of the propagation portion, and is connected to
the surface of the piezoelectric element through a contact medium.
The propagation redirecting portion includes a slope inclined in a
vertical direction to the surface of the piezoelectric element,
reflects the ultrasonic wave incident on the propagation
redirecting portion from the piezoelectric element on the slope and
emits to the propagation portion, reflects the ultrasonic wave on
the slope which is reflected on an end surface on the other side in
the extending direction of the propagation portion and incident on
the propagation redirecting portion from the propagation portion
and emits to the piezoelectric element.
[0009] According to the invention, both thinning of an ultrasonic
sensor and securing of measurement accuracy of a thickness of a
subject can be achieved while a calibration piece is assembled to
an ultrasonic sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a diagram schematically illustrating a
configuration of an ultrasonic inspection system in a first
embodiment of the invention together with a pipe (subject);
[0011] FIG. 2 is a top view illustrating a structure of an
ultrasonic sensor in the first embodiment of the invention;
[0012] FIG. 3 is a diagram viewed from a direction of arrow III in
FIG. 2;
[0013] FIG. 4 is a diagram illustrating a specific example of a
receiving waveform in the first embodiment of the invention;
[0014] FIG. 5 is a flowchart illustrating a processing procedure of
a control device in the first embodiment of the invention;
[0015] FIG. 6 is a diagram for describing a tilt angle of a slope
of a propagation redirecting portion of the calibration piece in
the first embodiment of the invention;
[0016] FIG. 7 is a top view illustrating a structure of the
ultrasonic sensor in a second embodiment of the invention;
[0017] FIG. 8 is a diagram viewed from a direction of arrow VIII in
FIG. 7;
[0018] FIG. 9 is a diagram illustrating a specific example of a
receiving waveform in the second embodiment of the invention;
[0019] FIG. 10 is a flowchart illustrating a processing procedure
of a control device in the second embodiment of the invention;
[0020] FIG. 11 is a top view illustrating a structure of the
ultrasonic sensor in a third embodiment of the invention;
[0021] FIG. 12 is a diagram viewed from a direction of arrow XII in
FIG. 11;
[0022] FIG. 13 is a diagram viewed from a direction of arrow XIII
in FIG. 11;
[0023] FIG. 14 is a top view illustrating a structure of the
ultrasonic sensor in a fourth embodiment of the invention;
[0024] FIG. 15 is a diagram viewed from a direction of arrow XV in
FIG. 14;
[0025] FIG. 16 is a top view illustrating a structure of the
ultrasonic sensor in a fifth embodiment of the invention;
[0026] FIG. 17 is a diagram viewed from a direction of arrow XVII
in FIG. 16; and
[0027] FIG. 18 is a diagram viewed from a direction of arrow XVIII
in FIG. 16.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] A first embodiment of the invention will be described with
reference the drawings.
[0029] FIG. 1 is a diagram schematically illustrating a
configuration of an ultrasonic inspection system in this embodiment
together with a pipe (subject). FIG. 2 is a top view illustrating a
structure of the ultrasonic sensor in this embodiment. FIG. 3 is a
diagram viewed from a direction of arrow III in FIG. 2.
[0030] A pipe 20 (subject) of this embodiment is made of, for
example, carbon steel or stainless steel, and is heated to a high
temperature while liquid and gas flow therein during the operation
of a plant. Therefore, the pipe is covered with a heat insulating
material 21 made of, for example, calcium silicate, rock wool,
glass wool, amorphous water-kneading material, or rigid urethane
foam.
[0031] The ultrasonic inspection system of this embodiment includes
an ultrasonic sensor 1, a control device 2, and a display device 3
(display). The ultrasonic sensor 1 is fixed to the surface of the
pipe 20 below the heat insulating material 21 through a heat
resistant adhesive 4 (contact medium).
[0032] The ultrasonic sensor 1 includes a piezoelectric element 5
and the calibration piece 6 which is bonded to the upper surface
(that is, a surface on the opposite side to the subject) of the
piezoelectric element 5. The piezoelectric element 5 is made of a
piezoelectric ceramic such as lead zirconate titanate. A material
of the calibration piece 6 is desirably the same as the material of
the pipe 20 (carbon steel or stainless steel), or may be ceramics
such as aluminum, lead, titan, brass, or alumina.
[0033] The calibration piece 6 includes the propagation portion 7
of a square column shape extending in a direction (the right and
left direction in FIGS. 2 and 3) along the upper surface of the
piezoelectric element 5, and a propagation redirecting portion 8
which is formed in one side (the left side in FIGS. 2 and 3) in the
extending direction of the propagation portion 7 and in a
triangular column shape connected to the piezoelectric element 5
through the heat resistant adhesive 4 (see FIG. 6 below) Further,
in FIG. 3, the propagation portion 7 of the calibration piece 6 is
separated from the upper surface of the piezoelectric element 5,
but the invention is not limited. In other words, even if the
propagation portion 7 of the calibration piece 6 and the upper
surface of the piezoelectric element 5 are adjacent, but an
extremely-thin air layer exists therebetween, an ultrasonic wave is
not propagated. Therefore, the contact medium does desirably not
exist (this is true in the propagation portion of the other
embodiments below).
[0034] The propagation redirecting portion 8 includes a slope 9
which is inclined in a vertical direction to the upper surface of
the piezoelectric element 5. Then, as illustrated with arrow A1 in
in FIGS. 2 and 3, the ultrasonic wave incident on the propagation
redirecting portion 8 from the piezoelectric element 5 is reflected
on the slope 9 and emitted toward the propagation portion 7. As
illustrated with arrow A2 in FIGS. 2 and 3, the ultrasonic wave
which is reflected on an end surface 10 on the other side (the
right side in FIGS. 2 and 3) in the extending direction of the
propagation portion 7 and incident from the propagation portion 7
to the propagation redirecting portion 8 is reflected on the slope
9 and emitted toward the piezoelectric element 5.
[0035] The control device 2 includes a pulsar 11, a receiver 12, a
signal processing unit 13, and a memory unit 14. Further, the
signal processing unit 13 is configured by a processor which
performs a process according to a program. The memory unit 14 is
configured by a hard disk and a memory.
[0036] The piezoelectric element 5 of the ultrasonic sensor 1
vibrates in a thickness direction by a drive signal (electrical
signal) from the pulsar 11 of the control device 2, and transmits
the ultrasonic wave to the calibration piece 6 and the pipe 20. In
addition, the piezoelectric element 5 receives the ultrasonic wave
A reflected one time on the end surface of the calibration piece 6
as illustrated with arrows A1 and A2 in FIG. 3, and the ultrasonic
wave B reflected one time on the inner surface of the pipe 20 as
illustrated with arrows B1 and B2 in FIG. 3. Then, the received
ultrasonic waves A and B into a waveform signal (electrical signal)
and are output to the receiver 12 of the control device 2.
[0037] The signal processing unit 13 of the control device 2
performs a predetermined process (specifically, a conversion
process from an analog signal to a digital signal) on the waveform
signal obtained through the receiver 12. With this configuration,
as illustrated in FIG. 4, waveform data of the ultrasonic waves A
and B is acquired. Then, the waveform data is output and stored in
the memory unit 14, and output and displayed in the display device
3.
[0038] A processing content of the control device 2 of this
embodiment will be described. FIG. 5 is a flowchart illustrating a
processing procedure of the control device 2 in this
embodiment.
[0039] In step S1, the pulsar 11 of the control device 2 outputs
the drive signal to the piezoelectric element 5 of the ultrasonic
sensor 1, and transmits the ultrasonic wave from the piezoelectric
element 5. Thereafter, the piezoelectric element 5 receives the
ultrasonic waves A and B, and converts the waves into the waveform
signals and outputs to the receiver 12 of the control device 2. The
signal processing unit 13 of the control device 2 performs a
predetermined process on the waveform signal obtained through the
receiver 12, and acquires the waveform data of the ultrasonic waves
A and B. Then, for example, timing when the drive signal is output
is set to a start point, and timing when the amplitude
(interpolated value) of each ultrasonic wave is maximized is set to
an end point. A propagation time ta of the ultrasonic wave A and a
propagation time tb of the ultrasonic wave B are measured.
[0040] Thereafter, the process proceeds to step S2. The signal
processing unit 13 calibrates a time axis (the start point of the
propagation time) on the basis of the propagation time ta of the
ultrasonic wave A, a propagation distance of the ultrasonic wave in
the calibration piece 6, and a sound speed of the calibration piece
6. Specifically, for example, a propagation time ta' of the
ultrasonic wave A is calculated from the propagation distance of
the ultrasonic wave in the calibration piece 6 and the sound speed
of the calibration piece 6. Then, it is determined whether a
difference between a measurement value ta of the propagation time
of the ultrasonic wave and a calculation value ta' falls within an
allowable range. In a case where the difference does not fall
within the allowable range, the time axis is calibrated to reduce
the difference. In other words, the propagation time tb of the
ultrasonic wave B measured in step S1 is corrected.
[0041] Thereafter, the process proceeds to step S3. The signal
processing unit 13 calculates a thickness H of the pipe 20 from the
propagation time tb of the ultrasonic wave B and a longitudinal
sound speed v of the pipe 20 which are obtained as described above.
The signal processing unit 13 outputs and stores the calculated
thickness H of the pipe 20 to the memory unit 14, and outputs and
displays the thickness to the display device 3.
[0042] An operational effect of this embodiment configured as
described above will be described. The calibration piece 6 of this
embodiment includes the propagation redirecting portion 8 which
switches a propagation direction of the ultrasonic wave to a
direction along the upper surface of the piezoelectric element 5.
With this configuration, the length of the calibration piece 6 in a
parallel direction to the upper surface of the piezoelectric
element 5 is increased instead of the height of the calibration
piece 6 in a vertical direction to the upper surface of the
piezoelectric element 5. Therefore, a reception timing of the
ultrasonic wave A reflected one time on the end surface 10 of the
calibration piece 6 can be delayed from a reception timing of the
ultrasonic wave B reflected one time on the inner surface of the
pipe 20 (see FIG. 4). Therefore, both the thinning of the
ultrasonic sensor 1 and the securing of measurement accuracy of the
thickness of the pipe 20 can be achieved while the calibration
piece 6 is assembled to the ultrasonic sensor 1.
[0043] A design method of the calibration piece 6 of this
embodiment will be supplemented.
[0044] As illustrated in FIG. 6, a tilt angle a (specifically, an
angle between the upper surface of the piezoelectric element 5 and
the slope 9) of the slope 9 of the propagation redirecting portion
8 of the calibration piece 6 is the same as the incident angle of
the ultrasonic wave from the piezoelectric element 5 onto the slope
9. The ultrasonic wave reflected on the slope 9 of the propagation
redirecting portion 8 is desirably propagated in the extending
direction of the propagation portion 7 (that is, the parallel
direction to the upper surface of the piezoelectric element 5).
Therefore, if a reflection angle of the ultrasonic wave from the
piezoelectric element 5 on the slope 9 is .beta.,
.alpha.+.beta.=90.degree. is desirable satisfied.
[0045] For example, in a case where a longitudinal wave is used as
the ultrasonic wave incident on the slope 9 from the piezoelectric
element 5, and a longitudinal wave is used as the ultrasonic wave
reflected on the slope 9, .alpha.=.beta. is satisfied. Therefore,
.alpha.=45.degree. is satisfied.
[0046] On the other hand, for example, in a case where a
longitudinal wave is used as the ultrasonic wave incident on the
slope 9 from the piezoelectric element 5, and a transversal wave is
used as the ultrasonic wave reflected and converted on the slope 9,
the tilt angle a is calculated using the following Expression (1).
v1 in the expression represents a longitudinal sound speed of the
calibration piece 6, and vs represents a transversal sound speed of
the calibration piece 6.
sin .alpha./sin(90.degree.-.alpha.)=v1/vs (1)
[0047] Since the longitudinal sound speed v1 and the transversal
sound speed vs are different depending on the material of the
calibration piece 6, the tilt angle a is changed. In a case where
the material of the calibration piece 6 is alumina, the tilt angle
satisfies .alpha.=59.degree.. In a case where the material of the
calibration piece 6 is carbon steel or stainless steel, the tilt
angle satisfies .alpha.=62.degree.. In a case where the material of
the calibration piece 6 is titan, the tilt angle
.alpha.=63.degree.. In a case where the material of the calibration
piece 6 is aluminum, the tilt angle satisfies .alpha.=64.degree..
In a case where the material of the calibration piece 6 is brass,
the tilt angle satisfies .alpha.=65.degree.. In a case where the
material of the calibration piece 6 is lead, the tilt angle
satisfies .alpha.=72.degree..
[0048] According to preliminary studies, even if the tilt angle
.alpha. of the slope 9 of the propagation redirecting portion 8 is
deviated by about .+-.5.degree. with respect to an optimal value
calculated using Expression (1), it can be seen that the ultrasonic
wave reflected on the slope 9 is propagated in the propagation
portion 7 at a sufficient SN ratio. Therefore, for example, in a
case where a longitudinal wave is used as the ultrasonic wave
incident on the slope 9 from the piezoelectric element 5, and a
longitudinal wave is used as the ultrasonic wave reflected on the
slope 9, the tilt angle may satisfy .alpha.=40.degree.. In
addition, for example, in a case where a longitudinal wave is used
as the ultrasonic wave incident on the slope 9 from the
piezoelectric element 5, a transversal wave is used as the
ultrasonic wave reflected on the slope 9, and the material of the
calibration piece 6 is lead, the tilt angle may satisfy
.alpha.=77.degree.. Therefore, the tilt angle a falls within a
range of 40.degree. to 77.degree..
[0049] As illustrated in FIG. 3, if a one-way propagation distance
of the ultrasonic wave between the upper surface of the
piezoelectric element 5 and the slope 9 of the calibration piece 6
(herein, the center position of the slope 9 in the height direction
and the length direction of the calibration piece 6 is used as a
representative position, which is true in the following
description) is set to L1, and a one-way propagation distance of
the ultrasonic wave between the slope 9 and the end surface 10 of
the calibration piece 6 is set to L2, the propagation distance of
the ultrasonic wave in the calibration piece 6 is represented by
(L1+L2).times.2. In other words, the propagation distance of the
ultrasonic wave in the calibration piece 6 is represented by
(Height of Propagation Redirecting Portion 8/2+Length of
Propagation Redirecting Portion 8/2+Length of Propagation Portion
7).times.2.
[0050] Assuming L1=0 because L1 is small, if the longitudinal wave
is used as an ultrasonic wave propagating between the slope 9 and
the end surface 10 of the calibration piece 6, the propagation time
of the ultrasonic wave ta in the calibration piece 6 is represented
by L2.times.2/v1. On the other hand, if the transversal wave is
used as an ultrasonic wave propagating between the slope 9 and the
end surface 10 of the calibration piece 6, the propagation time of
the ultrasonic wave ta in the calibration piece 6 is represented by
L2.times.2/vs. The propagation time of the ultrasonic wave tb in
the pipe 20 is represented by H.times.2/v.
[0051] Therefore, if the longitudinal wave is used as an ultrasonic
wave propagating between the slope 9 and the end surface 10 of the
calibration piece 6, it is desirable that the condition
L2>H.times.v1/v is satisfied in order to satisfy a relation of
ta>tb. On the other hand, if the transversal wave is used as an
ultrasonic wave propagating between the slope 9 and the end surface
10 of the calibration piece 6, it is desirable that the condition
L2>H.times.vs/v is satisfied in order to satisfy a relation of
ta>tb. From this viewpoint of view, it is desirable even for the
length of the propagation portion 7 in the right and left direction
in FIGS. 2 and 3 to satisfy the condition of becoming larger than
H.times.v1/v or the condition of becoming larger than H.times.vs/v.
In general, v1<vs is satisfied. Therefore, if the latter
condition is satisfied, the former condition is also satisfied.
[0052] Further, in FIG. 4, in a case where the longitudinal wave is
used as the ultrasonic wave propagating between the upper surface
of the piezoelectric element 5 and the slope 9 of the calibration
piece 6, and the transversal wave is used as the ultrasonic wave
propagating between the slope 9 and the end surface 10 of the
calibration piece 6, the material of the calibration piece 6 is
carbon steel, and the tilt angle .alpha. is set to 62.degree.. In
addition, the material of the pipe 20 is the same as that of the
calibration piece 6, the thickness H of the pipe 20 is set to 8.5
mm, and the length of the propagation portion 7 of the calibration
piece 6 is set to 6.5 mm.
[0053] A second embodiment of the invention will be described using
FIGS. 7 to 10. Further, in this embodiment, the same portions as
those in the above embodiment will be assigned with the same
symbols, and the description will be appropriately omitted.
[0054] FIG. 7 is a top view illustrating a structure of the
ultrasonic sensor in this embodiment. FIG. 8 is a diagram viewed
from a direction of arrow VIII in FIG. 7.
[0055] The propagation portion 7 of the calibration piece 6 of this
embodiment includes end surfaces 10A and 10B on the other sides
(the right side in FIGS. 7 and 8) in the extending direction. If a
one-way propagation distance of the ultrasonic wave between the
slope 9 and the end surface 10A of the calibration piece 6 is set
to L3, and a one-way propagation distance of the ultrasonic wave
between the slope 9 and the end surface 10B of the calibration
piece 6 is set to L4, L3<L4 is satisfied.
[0056] Further, if the longitudinal wave is used as the ultrasonic
wave propagating between the slope 9 and the end surfaces 10A and
10B of the calibration piece 6, the condition of L3>H.times.v1/v
is desirable satisfied. On the other hand, if the transversal wave
is used as the ultrasonic wave propagating between the slope 9 and
the end surfaces 10A and 10B of the calibration piece 6, the
condition of L3>H.times.vs/v is desirably satisfied. From this
viewpoint of view, it is desirable even for the length of the
propagation portion 7 from the end surface 10A to satisfy the
condition of becoming larger than H.times.v1/v or the condition of
becoming larger than H.times.vs/v. In general, v1<vs is
satisfied. Therefore, if the latter condition is satisfied, the
former condition is also satisfied.
[0057] In addition, if the longitudinal wave is used as the
ultrasonic wave propagating between the slope 9 and the end
surfaces 10A and 10B of the calibration piece 6, the length of the
longitudinal wave of the calibration piece 6 is set to .lamda.1,
the condition of (L4-L3)>.lamda.1 is set to be satisfied. On the
other hand, if the transversal wave is used as the ultrasonic wave
propagating between the slope 9 and the end surfaces 10A and 10B of
the calibration piece 6, the length of the transversal wave of the
calibration piece 6 is set to .lamda.s, the condition of
(L4-L3)>.lamda.s is set to be satisfied.
[0058] The piezoelectric element 5 receives the ultrasonic wave B
reflected one time on the inner surface of the pipe 20 as
illustrated with arrows B1 and B2 in FIG. 8, the ultrasonic wave C
reflected one time on the end surface 10A of the calibration piece
6 as illustrated with arrows C1 and C2 in FIGS. 7 and 8, and the
ultrasonic wave D reflected one time on the end surface 10B of the
calibration piece 6 as illustrated with arrows D1 and D2 in FIGS. 7
and 8. Then, the received ultrasonic waves B, C, and D are
converted into the waveform signal and are output to the receiver
12 of the control device 2.
[0059] The signal processing unit 13 of the control device 2
performs a predetermined process on the waveform signal obtained
through the receiver 12. With this configuration, as illustrated in
FIG. 9, the waveform data of the ultrasonic waves B, C, and D is
acquired. Then, the waveform data is output and stored in the
memory unit 14, and output and displayed in the display device
3.
[0060] A processing content of the control device 2 of this
embodiment will be described. FIG. 10 is a flowchart illustrating a
processing procedure of the control device 2 in this
embodiment.
[0061] In step S1, the pulsar 11 of the control device 2 outputs
the drive signal to the piezoelectric element 5 of the ultrasonic
sensor 1, and transmits the ultrasonic wave from the piezoelectric
element 5. Thereafter, the piezoelectric element 5 receives the
ultrasonic waves B, C and D, and converts the waves into the
waveform signals and outputs to the receiver 12 of the control
device 2. The signal processing unit 13 of the control device 2
performs a predetermined process on the waveform signal obtained
through the receiver 12, and acquires the waveform data of the
ultrasonic waves B, C, and D. Then, for example, timing when the
drive signal is output is set to a start point, and timing when the
amplitude (interpolated value) of each ultrasonic wave is maximized
is set to an end point. The propagation time tb of the ultrasonic
wave B, a propagation time tc of the ultrasonic wave C, and a
propagation time td of the ultrasonic wave D are measured.
[0062] Thereafter, the process proceeds to step S4. The signal
processing unit 13 calculates the sound speed of the calibration
piece 6 from the propagation time tc and the propagation distance
of the ultrasonic wave C reflected on the end surface 10A of the
calibration piece 6. Specifically, for example, if a distance
expressed by (L1+L3).times.2 is used as the propagation distance of
the ultrasonic wave C reflected on the end surface 10A of the
calibration piece 6, the longitudinal wave is used as the
ultrasonic wave propagating between the upper surface of the
piezoelectric element 5 and the slope 9 of the calibration piece 6,
and the longitudinal wave is used as the ultrasonic wave
propagating between the slope 9 and the end surface 10A of the
calibration piece 6, the longitudinal sound speed v1 of the
calibration piece 6 is calculated from the propagation time tc and
the propagation distance of the ultrasonic wave C.
[0063] Alternatively, for example, assuming L1=0, if a distance
expressed by L3.times.2 is used as the propagation distance of the
ultrasonic wave C reflected on the end surface 10A of the
calibration piece 6, and the longitudinal wave is used as the
ultrasonic wave propagating between the slope 9 and the end surface
10 of the calibration piece 6, the longitudinal sound speed v1 of
the calibration piece 6 is calculated from the propagation time tc
and the propagation distance of the ultrasonic wave C. In addition,
for example, assuming L1=0, if a distance expressed by L3.times.2
is used as the propagation distance of the ultrasonic wave C
reflected on the end surface 10A of the calibration piece 6, and
the transversal wave is used as the ultrasonic wave propagating
between the slope 9 and the end surface 10 of the calibration piece
6, the transversal sound speed vs of the calibration piece 6 is
calculated from the propagation time tc and the propagation
distance of the ultrasonic wave C.
[0064] The signal processing unit 13 corrects the longitudinal
sound speed v of the pipe 20 on the basis of the calculated sound
speed of the calibration piece 6 (specifically, the longitudinal
sound speed v1 or the transversal sound speed vs). Making an
explanation in detail, in a case where the material of the
calibration piece 6 is the same as the material of the pipe 20, the
temperature of the calibration piece 6 and the temperature of the
pipe 20 are considered as the same. Therefore, the longitudinal
sound speed v of the pipe 20 is the same as the calculated
longitudinal sound speed v1 of the calibration piece 6.
Alternatively, if a longitudinal sound speed v1 is calculated from
the calculated transversal sound speed vs of the calibration piece
6 using a relational expression between the transversal sound speed
vs and the longitudinal sound speed v1 of the calibration piece 6
which are created in advance, the longitudinal sound speed v of the
pipe 20 is the same as the calculated longitudinal sound speed v1
of the calibration piece 6.
[0065] In a case where the material of the calibration piece is
different from the material of the pipe 20, the temperature of the
calibration piece 6 is calculated from the calculated sound speed
of the calibration piece 6 using a relational expression between
the sound speed of the calibration piece 6 and the temperature of
the calibration piece 6 which are created in advance, and the
temperature of the calibration piece 6 and the temperature of the
pipe 20 are considered as the same. Then, the longitudinal sound
speed v of the pipe 20 is calculated from the calculated
temperature of the pipe 20 using the relational expression between
the temperature of the pipe 20 and the longitudinal sound speed v
of the pipe 20 which are created in advance.
[0066] Thereafter, the process proceeds to step S2. The signal
processing unit 13 calibrates the time axis (specifically, the
start point of the propagation time) on the basis of the
propagation time td and the propagation distance of the ultrasonic
wave D reflected on the end surface 10B of the calibration piece 6
and the sound speed of the calibration piece 6. Specifically, for
example, a propagation time td' of the ultrasonic wave D is
calculated from the propagation distance of the ultrasonic wave D
reflected on the end surface 10B of the calibration piece 6
(specifically, for example, a distance expressed by (L1+L4).times.2
or a distance expressed by L4.times.2) and the sound speed of the
calibration piece 6. Then, it is determined whether a difference
between a measurement value td of the propagation time of the
ultrasonic wave and a calculation value td' falls within an
allowable range. In a case where the difference does not fall
within the allowable range, the time axis is calibrated to reduce
the difference. In other words, the propagation time tb of the
ultrasonic wave B acquired in step S1 is corrected.
[0067] Thereafter, the process proceeds to step S3. The signal
processing unit 13 calculates a thickness H of the pipe 20 from the
propagation time tb of the ultrasonic wave B and a longitudinal
sound speed v of the pipe 20 which are obtained as described above.
The signal processing unit 13 outputs and stores the calculated
thickness H of the pipe 20 to the memory unit 14, and outputs and
displays the thickness to the display device 3.
[0068] An operational effect of this embodiment configured as
described above will be described. Similarly to the first
embodiment, the calibration piece 6 of this embodiment also
includes the propagation redirecting portion 8 which switches a
propagation direction of the ultrasonic wave to a direction along
the upper surface of the piezoelectric element 5. With this
configuration, the length of the calibration piece 6 in a parallel
direction to the upper surface of the piezoelectric element 5 is
increased instead of the height of the calibration piece 6 in a
vertical direction to the upper surface of the piezoelectric
element 5. Therefore, a reception timing of the ultrasonic wave C
reflected one time on the end surface 10A of the calibration piece
6 and a reception timing of the ultrasonic wave D reflected one
time on the end surface 10B of the calibration piece 6 can be
delayed from a reception timing of the ultrasonic wave B reflected
one time on the inner surface of the pipe 20 (see FIG. 9).
Therefore, both the thinning of the ultrasonic sensor 1 and the
securing of measurement accuracy of the thickness of the pipe 20
can be achieved while the calibration piece 6 is assembled to the
ultrasonic sensor 1.
[0069] In addition, in this embodiment, it is possible to correct
the sound speeds of the calibration piece 6 and the pipe 20 without
using a temperature sensor which detects the calibration piece 6
and the temperature of the pipe 20. Therefore, the thickness of the
pipe 20 can be measured with a high measurement accuracy with a
simple configuration.
[0070] A third embodiment of the invention will be described using
FIGS. 11 to 13. Further, in this embodiment, the same portions as
those in the above embodiment will be assigned with the same
symbols, and the description will be appropriately omitted.
[0071] FIG. 11 is a top view illustrating a structure of the
ultrasonic sensor in this embodiment. FIG. 12 is a diagram viewed
from a direction of arrow XII in FIG. 11. FIG. 13 is a diagram
viewed from a direction of arrow XIII in FIG. 11.
[0072] The calibration piece 6 of this embodiment includes the
propagation portion 7A of the square column shape extending in one
direction (the right and left direction in FIGS. 11 and 12) along
the upper surface of the piezoelectric element 5, the propagation
portion 7B of the square column shape extending in the other
direction (the up and down direction in FIG. 11, and the right and
left direction in FIG. 13) along the upper surface of the
piezoelectric element 5, a propagation direction changing unit 15
of the triangular column shape disposed between the propagation
portions 7A and 7B, and the propagation redirecting portion 8 of
the triangular column shape which is formed in one side (the left
side in FIGS. 11 and 12) in the extending direction of the
propagation portion 7A and connected to the piezoelectric element 5
through the heat resistant adhesive 4.
[0073] The propagation redirecting portion 8 includes the slope 9
which is inclined in the vertical direction to the upper surface of
the piezoelectric element 5. The propagation direction changing
unit 15 includes a slope 16 which is inclined in the parallel
direction to the upper surface of the piezoelectric element 5.
Then, as illustrated with arrows E1 and E2 in FIGS. 11 and 12, the
ultrasonic wave incident on the propagation redirecting portion 8
from the piezoelectric element 5 is reflected on the slope 9 and
emitted toward the propagation portion 7A. The ultrasonic wave
incident on the propagation direction changing unit 15 from the
propagation portion 7A is reflected on the slope 16 and emitted
toward the propagation portion 7B. In addition, as illustrated with
arrows E3 and E4 in FIGS. 11 and 13, the ultrasonic wave which is
reflected on the end surface 10 on the other side (the upper side
in FIG. 11, and the right side in FIG. 13) in the extending
direction of the propagation portion 7B and incident on the
propagation direction changing unit 15 from the propagation portion
7B is reflected on the slope 16 and emitted toward the propagation
portion 7A. The ultrasonic wave incident on the propagation
redirecting portion 8 from the propagation portion 7A is reflected
on the slope 9 and emitted toward the piezoelectric element 5.
[0074] If the longitudinal wave is used as the ultrasonic wave
propagating between the slope 9 and the slope 16 and between the
slope 16 and the end surface 10 of the calibration piece 6, and a
one-way propagation distance of the ultrasonic wave between the
slope 9 and the slope 16 of the calibration piece 6 (herein, the
center position of the slope 16 in a width direction and a length
direction of the calibration piece 6 is used as a representative
position, which is true in the following description) is set to L5,
and a one-way propagation distance of the ultrasonic wave between
the slope 16 and the end surface 10 of the calibration piece 6 is
set to L6, the condition of (L5+L6)>H.times.v1/v is desirably
satisfied. On the other hand, if the transversal wave is used as
the ultrasonic wave propagating between the slope 9 and the slope
16 and between the slope 16 and the end surface 10 of the
calibration piece 6, the condition of (L5+L6)>H.times.vs/v is
desirably satisfied.
[0075] The piezoelectric element 5 receives the ultrasonic wave B
reflected one time on the inner surface of the pipe 20 as
illustrated with arrows B1 and B2 in FIGS. 12 and 13, and the
ultrasonic wave E reflected one time on the end surface 10 of the
calibration piece 6 as illustrated with arrows E1 to E4 in FIGS. 11
to 13. Then, the received ultrasonic waves B and E are converted
into the waveform signal and are output to the receiver 12 of the
control device 2.
[0076] Similarly to the first embodiment, the control device 2
calibrates the propagation time of the ultrasonic wave E
propagating in the calibration piece 6 and the time axis on the
basis of the sound speed of the calibration piece 6, and calculates
the thickness H of the pipe 20 on the basis of the propagation time
of the ultrasonic wave B propagating in the pipe 20 and the
longitudinal sound speed v of the pipe 20. Then, the calculated
thickness H of the pipe 20 is output and stored in the memory unit
14, and output and displayed in the display device 3.
[0077] An operational effect of this embodiment configured as
described above will be described. Similarly to the first
embodiment, the calibration piece 6 of this embodiment also
includes the propagation redirecting portion 8 which switches a
propagation direction of the ultrasonic wave to a direction along
the upper surface of the piezoelectric element 5. With this
configuration, the length of the calibration piece 6 in a parallel
direction to the upper surface of the piezoelectric element 5 is
increased instead of the height of the calibration piece 6 in a
vertical direction to the upper surface of the piezoelectric
element 5. Therefore, a reception timing of the ultrasonic wave E
reflected one time on the end surface 10 of the calibration piece 6
can be delayed from a reception timing of the ultrasonic wave B
reflected one time on the inner surface of the pipe 20. Therefore,
both the thinning of the ultrasonic sensor 1 and the securing of
measurement accuracy of the thickness of the pipe 20 can be
achieved while the calibration piece 6 is assembled to the
ultrasonic sensor 1. In addition, the ultrasonic sensor 1 in this
embodiment can be minimized compared to the first embodiment.
[0078] Further, in the third embodiment, the propagation portion 7B
of the calibration piece 6 has been described as an example in case
where one end surface 10 is included similarly to the first
embodiment, but the invention is not limited thereto. Similarly to
the second embodiment, two end surfaces 10A and 10B may be
included. Then, the control device 2 may perform the similar
process as the second embodiment.
[0079] A fourth embodiment of the invention will be described using
FIGS. 14 and 15. Further, in this embodiment, the same portions as
those in the above embodiment will be assigned with the same
symbols, and the description will be appropriately omitted.
[0080] FIG. 14 is a top view illustrating a structure of the
ultrasonic sensor in this embodiment. FIG. 15 is a diagram viewed
from a direction of arrow XV in FIG. 14.
[0081] The calibration piece 6 of this embodiment includes the
propagation portion 7 of the square column shape extending in one
direction (the right and left direction in FIGS. 14 and 15) along
the upper surface of the piezoelectric element 5, a propagation
redirecting portion 8A of the triangular column shape which is
formed on one side (the left side in FIGS. 14 and 15) of the
extending direction of the propagation portion 7 and connected to
the piezoelectric element 5 through the heat resistant adhesive 4,
and a propagation redirecting portion 8B of the triangular column
shape which is formed on the other side (the right side in FIGS. 14
and 15) of the extending direction of the propagation portion 7 and
connected to the piezoelectric element 5 through the heat resistant
adhesive 4.
[0082] The propagation redirecting portions 8A and 8B include
respectively slopes 9A and 9B inclined in the vertical direction to
the upper surface of the piezoelectric element 5. Then, as
illustrated with arrow F1 in FIGS. 14 and 15, the ultrasonic wave
incident on the propagation redirecting portion 8A from the
piezoelectric element 5 is reflected on the slope 9A and emitted
toward the propagation portion 7. The ultrasonic wave incident on
the propagation redirecting portion 8B from the propagation portion
7 is reflected on the slope 9B and emitted toward the piezoelectric
element 5. In addition, as illustrated with arrow F2 in FIGS. 14
and 15, the ultrasonic wave incident on the propagation redirecting
portion 8B from the piezoelectric element 5 is reflected on the
slope 9B and emitted toward the propagation portion 7. The
ultrasonic wave incident on the propagation redirecting portion 8A
from the propagation portion 7 is reflected on the slope 9A and
emitted toward the piezoelectric element 5.
[0083] If the longitudinal wave is used as the ultrasonic wave
propagating between the slope 9A and the slope 9B of the
calibration piece 6, and a one-way propagation distance of the
ultrasonic wave between the upper surface of the piezoelectric
element 5 and the slope 9A or 9B of the calibration piece 6 is set
to L1, and a one-way propagation distance of the ultrasonic wave
between the slope 9A and the slope 9B of the calibration piece 6 is
set to L7, the condition of L7>H.times.2.times.v1/v is desirably
satisfied. On the other hand, if the transversal wave is used as
the ultrasonic wave propagating between the slope 9A and the slope
9B of the calibration piece 6, the condition of
L7>H.times.2.times.vs/v is desirably satisfied.
[0084] The piezoelectric element 5 receives the ultrasonic wave B
reflected one time on the inner surface of the pipe 20 as
illustrated with arrows B1 and B2 in FIG. 15, and the ultrasonic
wave F propagating in the calibration piece 6 as illustrated with
arrows F1 and F2 in FIGS. 14 and 15. Then, the received ultrasonic
waves B and F are converted into the waveform signal and are output
to the receiver 12 of the control device 2.
[0085] Similarly to the first embodiment, the control device 2
calibrates the propagation time of the ultrasonic wave F
propagating in the calibration piece 6 and the time axis on the
basis of the sound speed of the calibration piece 6, and calculates
the thickness H of the pipe 20 on the basis of the propagation time
of the ultrasonic wave B propagating in the pipe 20 and the
longitudinal sound speed v of the pipe 20. Then, the calculated
thickness H of the pipe 20 is output and stored in the memory unit
14, and output and displayed in the display device 3.
[0086] An operational effect of this embodiment configured as
described above will be described. The calibration piece 6 of this
embodiment includes the propagation redirecting portions 8A and 8B
which switches a propagation direction of the ultrasonic wave to a
direction along the upper surface of the piezoelectric element 5.
With this configuration, the length of the calibration piece 6 in a
parallel direction to the upper surface of the piezoelectric
element 5 is increased instead of the height of the calibration
piece 6 in a vertical direction to the upper surface of the
piezoelectric element 5. Therefore, a reception timing of the
ultrasonic wave F propagating in the calibration piece 6 can be
delayed from a reception timing of the ultrasonic wave B reflected
one time on the inner surface of the pipe 20. Therefore, both the
thinning of the ultrasonic sensor 1 and the securing of measurement
accuracy of the thickness of the pipe 20 can be achieved while the
calibration piece 6 is assembled to the ultrasonic sensor 1.
[0087] A fifth embodiment of the invention will be described using
FIGS. 16 to 18. Further, in this embodiment, the same portions as
those in the above embodiment will be assigned with the same
symbols, and the description will be appropriately omitted.
[0088] FIG. 16 is a top view illustrating a structure of the
ultrasonic sensor in this embodiment. FIG. 17 is a diagram viewed
from a direction of arrow XVII in FIG. 16. FIG. 18 is a diagram
viewed from a direction of arrow XVIII in FIG. 16.
[0089] The calibration piece 6 of this embodiment includes the
propagation portion 7A of the square column shape extending in one
direction (the right and left direction in FIGS. 16 and 17) along
the upper surface of the piezoelectric element 5, the propagation
portion 7B of the square column shape extending in the other
direction (the up and down direction in FIG. 16, and the right and
left direction in FIG. 18) along the upper surface of the
piezoelectric element 5, a propagation direction changing unit 15
of the triangular column shape disposed between the propagation
portions 7A and 7B, the propagation redirecting portion 8A of the
triangular column shape which is formed in one side (the left side
in FIGS. 16 and 17) in the extending direction of the propagation
portion 7A and connected to the piezoelectric element 5 through the
heat resistant adhesive 4, and the propagation redirecting portion
8B of the triangular column shape which is formed on the other side
(the upper side in FIG. 16, and the right side in FIG. 18) of the
propagation portion 7B and connected to the piezoelectric element 5
through the heat resistant adhesive 4.
[0090] The propagation redirecting portions 8A and 8B include
respectively the slopes 9A and 9B which are inclined in the
vertical direction to the upper surface of the piezoelectric
element 5. The propagation direction changing unit 15 includes a
slope 16 which is inclined in the parallel direction to the upper
surface of the piezoelectric element 5. Then, as illustrated with
arrows G1 and G2 in FIGS. 16 to 18, the ultrasonic wave incident on
the propagation redirecting portion 8A from the piezoelectric
element 5 is incident on the slope 9A and emitted toward the
propagation portion 7A, the ultrasonic wave incident on the
propagation direction changing unit 15 from the propagation portion
7A is incident on the slope 16 and emitted toward the propagation
portion 7B, and the ultrasonic wave incident on the propagation
redirecting portion 8B from the propagation portion 7B is incident
on the slope 9B and emitted toward the piezoelectric element 5. In
addition, as illustrated with arrows G3 and G4 in FIGS. 11 to 13,
the ultrasonic wave incident on the propagation redirecting portion
8B from the piezoelectric element 5 is incident on the slope 9B and
emitted toward the propagation portion 7B, the ultrasonic wave
incident on the propagation direction changing unit 15 from the
propagation portion 7B is incident on the slope 16 and emitted
toward the propagation portion 7A, and the ultrasonic wave incident
on the propagation redirecting portion 8A from the propagation
portion 7A is incident on the slope 9A and emitted toward the
piezoelectric element 5.
[0091] If the longitudinal wave is used as the ultrasonic wave
propagating between the slope 9A and the slope 16 and between the
slope 16 and the slope 9B of the calibration piece 6, a one-way
propagation distance of the ultrasonic wave between the upper
surface of the piezoelectric element 5 and the slope 9A or 9B of
the calibration piece 6 is set to L1, a one-way propagation
distance of the ultrasonic wave between the slope 9A and the slope
16 of the calibration piece 6 is set to L8, and a one-way
propagation distance of the ultrasonic wave between the slope 16
and the slope 9B of the calibration piece 6 is set to L9, the
condition of (L8+L9)>H.times.2.times.v1/v is desirably
satisfied. On the other hand, if the transversal wave is used as
the ultrasonic wave propagating between the slope 9A and the slope
16 and between the slope 16 and the slope 9B of the calibration
piece 6, the condition of (L8+L9)>H.times.2.times.vs/v is
desirably satisfied.
[0092] The piezoelectric element 5 receives the ultrasonic wave B
reflected one time on the inner surface of the pipe 20 as
illustrated with arrows B1 and B2 in FIGS. 17 and 18, and the
ultrasonic wave G propagating in the calibration piece 6 as
illustrated with arrows G1 to G4 in FIGS. 16 to 18. Then, the
received ultrasonic waves B and G are converted into the waveform
signal and are output to the receiver 12 of the control device
2.
[0093] Similarly to the first embodiment, the control device 2
calibrates the propagation time of the ultrasonic wave G
propagating in the calibration piece 6 and the time axis on the
basis of the sound speed of the calibration piece 6, and calculates
the thickness H of the pipe 20 on the basis of the propagation time
of the ultrasonic wave B propagating in the pipe 20 and the
longitudinal sound speed v of the pipe 20. Then, the calculated
thickness H of the pipe 20 is output and stored in the memory unit
14, and output and displayed in the display device 3.
[0094] An operational effect of this embodiment configured as
described above will be described. Similarly to the fourth
embodiment, the calibration piece 6 of this embodiment also
includes the propagation redirecting portions 8A and 8B which
switch a propagation direction of the ultrasonic wave to a
direction along the upper surface of the piezoelectric element 5.
With this configuration, the length of the calibration piece 6 in a
parallel direction to the upper surface of the piezoelectric
element 5 is increased instead of the height of the calibration
piece 6 in a vertical direction to the upper surface of the
piezoelectric element 5. Therefore, a reception timing of the
ultrasonic wave G propagating in the calibration piece 6 can be
delayed from a reception timing of the ultrasonic wave B reflected
one time on the inner surface of the pipe 20. Therefore, both the
thinning of the ultrasonic sensor 1 and the securing of measurement
accuracy of the thickness of the pipe 20 can be achieved while the
calibration piece 6 is assembled to the ultrasonic sensor 1.
[0095] Further, in the third and fifth embodiments, the calibration
piece 6 have been described about an example in a case where there
are provided two propagation portions 7A and 7B and one propagation
direction changing unit 15 between the propagation portions 7A and
7B, but the invention is not limited thereto. In other words, the
calibration piece 6 may include three or more propagation portions
and two or more propagation direction changing units between the
propagation portions.
* * * * *